The generic class of materials described as substantially random interpolymers, and including materials such as ethylene and/or .alpha.-olefin/vinyl aromatic monomer interpolymers, are known in the art and offer a range of material structures and properties which makes them useful for varied applications.
Although of utility in their own right, industry is constantly seeking to improve the applicability of these interpolymers, for example to extend the temperature range of application. It is also desirable to develop technologies to provide improvements in processability or performance.
Fillers are frequently used to improve the stiffness of polymer compositions, or to decrease the coefficient of linear thermal expansion, or to decrease the overall cost of the polymer composition, or to impart additional performance characteristics to the materials such as ignition resistance. Filled ethylene/vinyl monomer interpolymer compositions have been disclosed in WO 99/00449, the entire contents of which are herein incorporated by reference. Typically, the filler is incorporated at levels ranging from 5 to 90 weight percent of the formulation, depending upon the filler density. In view of the wide ranges of desirable properties and uses for materials based on ethylene and or .alpha.-olefin/vinyl or vinylidene monomer interpolymers, it is desirable to provide new compositions showing enhanced ignition resistance.
We have now found that filled compositions comprising thermoplastic substantially random interpolymers which have been prepared by polymerizing ethylene and/or one or more .alpha.-olefin monomers with one or more vinyl or vinylidene aromatic monomers and/or one or more hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and optionally with other polymerizable ethylenically unsaturated monomer(s) can be blended with a further component to impart surprisingly enhanced ignition resistance, as compared to corresponding thermoplastic interpolymer compositions without this component. The articles made from the compositions of the present invention have a substantially enhanced ignition resistance while generally maintaining good elongation properties, such as strain at break, stress at break and energy at break.
Although styrene-containing polymers such as polystyrene are prone to ignition and smoke generation, we have surprisingly found that the compositions of the present invention comprising substantially random interpolymers (even including those with high styrene contents), are able to achieve smoke densities below that of poly (vinyl chloride) (PVC)-based materials, and equivalent to those of non-styrene containing polymers such as ethylene/vinyl acetate (EVA) and ethylene/octene copolymers. We have also surprisingly found that, unlike EVA compositions, when the compositions of the present invention are used in combination with a coupling agent, there is no big drop in tear strength at increased temperature. In addition, the coupled compositions of the present invention show a large reduction in Flexural Modulus resulting in improved flexibility, while maintaining a smooth surface on extrusion. This combination of ignition resistance and low smoke generation, high tear strength, good flexibility and smooth surface renders the materials excellent PVC replacements.
We have also surprisingly found that the compositions of the present invention comprising a substantially random interpolymer are able to maintain values of Shore D hardness and Limiting Oxygen Index (LOI), only achievable in an EVA-based formulation by adding a mixture of ethylene/propylene (EP) rubber and polypropylene.
We have also surprisingly found that with the compositions of the present invention, it is possible to replace some of an ignition resistant additive, such as alumina trihydrate (ATH) or magnesium hydroxide, with an inert filler, for example CaCO.sub.3 and still maintain the ignition resistance of the materials.
The compositions of the present invention can be used as blends with ignition resistant polystyrene and surprisingly, the incorporation of processing aids based on oxidized polyethylene still results in a viscosity drop.
Using the compositions of the present invention, it is also possible to vary the penetration properties of the fabricated articles made from the resulting blend by varying the levels of silane and peroxide in the composition.
Finally, we have found a surprising synergistic interaction of hindered amine stabilizers such as CGL 116 with ignition resistant additives such as ATH results in a lower LOI reading and improved UL-94 rating.
The compositions having enhanced ignition resistance comprise:
(A) from about 5 to about 90 weight percent by weight of at least one substantially random interpolymer prepared by polymerizing ethylene and /or one or more .alpha.-olefin monomers with one or more vinyl or vinylidene aromatic monomers, and optionally with other polymerizable ethylenically unsaturated monomer(s); PA1 (B) from about 10 to about 94.9 percent by weight of at least one filler selected from ammonium polyphosphate, magnesium hydroxide, calcium hydroxide, and aluminum trihydrate; and PA1 (C) at least one component selected from; PA1 wherein the amounts of (A), (B) and (C) are based on the total weight of (A), (B) and (C). If a coupling agent of (C)(3) is present then the coupling agent may couple at least a portion of at least one filler to at least a portion of at least one interpolymer. PA1 (1) at least one filler selected from talc, calcium carbonate, glass fibers, marble dust, cement dust, clay, feldspar, silica or glass, fumed silica, silicates, alumina, magnesium oxide, antimony oxide, zinc oxide, barium sulfate, aluminum silicate, calcium silicate, titanium oxides, glass microspheres, mica, clays, wollastonite, and chalk; PA1 (2) at least one metal borate selected from the metal borates of Group IIA, and, optionally, at least one processing aid selected from the group consisting of polydimethyl siloxane, organopolysiloxanes, tartaric acid, stearic acid, zinc stearic, waxes, and high melt flow polyolefins; PA1 (3) at least one initiator or at least one coupling agent selected from the group consisting of organic peroxides, silanes, titanates, zirconates, multifunctional vinyl compounds and organic azides; and PA1 (4) at least one hindered amine stabilizer. PA1 (a) interpolymers or polymers to other interpolymers or polymers; PA1 (b) fillers to other fillers; PA1 (c) fillers to interpolymer or polymers; or PA1 (d) combinations thereof. It is believed that the interpolymer is typically grafted onto the coupling agent via a vinyl group while an active polar group on the coupling agent usually binds the coupling agent to the filler. PA1 Varian VXR-300, standard .sup.1 H: PA1 Sweep Width, 5000 Hz PA1 Acquisition Time, 3.002 sec PA1 Pulse Width, 8 .mu.sec PA1 Frequency, 300 MHz PA1 Delay, 1 sec PA1 Transients, 16 PA1 (C Phenyl)=C.sub.7.1 +A.sub.7.1 -(1.5.times.A.sub.6.6) PA1 (C Aliphatic)=C.sub.al -(15.times.A.sub.6.6) PA1 s.sub.c =(C Phenyl)/5 PA1 e.sub.c =(C Aliphatic-(3.times.s.sub.c))/4 PA1 E=e.sub.c /(e.sub.c +s.sub.c) PA1 S.sub.c =s.sub.c /(e.sub.c +s.sub.c) PA1 where: s.sub.c and e.sub.c are styrene and ethylene proton fractions in the interpolymer, respectively, and S.sub.c and E are mole fractions of styrene monomer and ethylene monomer in the interpolymer, respectively. PA1 1) the Interpolymer and additives were dry-blended together. PA1 2) the mixing bowl was oil heated, and the oil bath was set at 120.degree. C. to 180.degree. C. PA1 3) 1000 g of the pre-blend were charged to the mixing bowl PA1 4) mixing time was typically 10 to 14 minutes. PA1 5) the melt temperature of the mix was about 105.degree. C. to 147.degree. C. PA1 6) the blend was removed from the bowl and cooled, chopped, and hot pressed into test specimens. PA1 l=length tested in meters PA1 D=outer diameter PA1 d=inner diameter PA1 R=measured resistance in M.OMEGA. PA1 D/d=ratio of diameters
(1) about 5 to about 50 weight percent by weight of at least one filler selected from talc, calcium carbonate, glass fibers, marble dust, cement dust, clay, feldspar, silica or glass, fumed silica, silicates, alumina, magnesium oxide, antimony oxide, zinc oxide, barium sulfate, aluminum silicate, calcium silicate, titanium oxides, glass microspheres, mica, clays, wollastonite, and chalk; or PA2 (2) about 0.5 to about 20 percent by weight of at least one metal borate selected from the metal borates of Group IIA, and, optionally, about 0.5 to about 10 percent by weight of at least one processing aid selected from the group consisting of polydimethyl siloxane, organopolysiloxanes, tartaric acid, stearic acid, zinc stearic, waxes, and high melt flow polyolefins; or PA2 (3) about 0.1 to about 15 percent by weight of at least one initiator or at least one coupling agent selected from the group consisting of organic peroxides, silanes, titanates, zirconates, multifunctional vinyl compounds and organic azides; or PA2 (4) about 0.1 to about 20 percent by weight of at least one hindered amine stabilizer;
In a further aspect, the present invention relates to fabricated articles made from such a composition, including those made by injection molding, compression molding, extrusion, or blow molding. Said articles are often in the form a film, sheet, a multilayered structure, a floor, wall, or ceiling covering, foams, fibers, electrical devices, or wire and cable assemblies.